WooCommerce Product Image Size - Won't Change

I am just starting to upload a few of my products to https://store.christiangays.com using WooCommerce.

The original single product image size was 600 x 600. I have changed it to 300 x 300 but it won't reduce in size. It's not actually a full 600 x 600 but it's much bigger than I want.

I have installed Regenerate Thumbnails and run it but it hasn't helped. Of course I have dumped cache multiple times but I just can't seem to make these single product images smaller.

Would appreciate any help.
Support access is granted.
Thank you.